Update .evergreen/setup.sh

Co-authored-by: Copilot <[email protected]>

Author: aclark4life

.evergreen/setup.sh

@@ -6,7 +6,7 @@ set -eux
 # On Evergreen jobs, "CI" will be set, and if "CI" is set, add
 # "/opt/python/Current/bin" to PATH to pick up `just` and `uv`.
 if [ "${CI:-}" == "true" ]; then
-    PATH_EXT="opt/python/Current/bin:\$PATH"
+    PATH_EXT="/opt/python/Current/bin:\$PATH"
 fi
 
 export PATH="$PATH_EXT"